BIO1M03 - Week 1 Lecture Notes

Lecture 1 Content:

What does it Mean to Say that Something is Alive?

  1. Cellular (membrane-bound cells)

  2. Process information (process hereditary information in genes + info from environment)

  3. Evolve

Exceptions:

  • Virus:

    • Not Cellular

    • Does process information

    • Does evolve

  • Mule:

    • Cellular

    • processes information

    • cannot evolve (sterile)

  • Droid:

    • Not cellular

    • Can process information

    • may/may not evolve?



Definition of Theory:

  • Explanation for broad class of phenomena/observations

  • supported by a wide body of evidence

  • NOT a speculation/guess

Three Theories —> Framework for Modern Biological Science:

Cell Theory

  • What are organisms made of?

  • Life is cellular:

    • 1660s - Hooke & Leeuwenhoek first to observe cells

  • Cells: highly organized compartment

    • bound by plasma membrane

    • containing concentrated chemicals in aqueous solution

Chromosome Theory of Inheritance

  • Hereditary information transmitted from one generation to next

Theory of Evolution by Natural Selection

  • Where organisms come from











Lecture 2 Content:

Definitions - Hypothesis, Experiment, Prediction:

  • Hypothesis: Testable statement, explains something observed

    • X (explanatory/independent variable) affects/impacts Y (response/dependent variable)

    • does not imply direction


  • Experiment: Test effect of factor on particular phenomenon

  • Prediction: Measurable/observable result, must be correct if hypothesis is valid

    • X (explanatory/independent variable) increases/decreases Y(response/dependent variable)

    • Implies direction


Two Competing Hypotheses - Cell Theory

  1. Spontaneous Generation:

    • Organisms could arise spontaneously under certain conditions

    • Bacteria & Fungi that spoil foods (~evidence?)

      • Spring to life from nonliving materials

  2. Cell Theory:

    • All Organisms are made of cells

    • All cells come from pre-existing cells

Louis Pasteur’s Experiment

  • Louis Pasteur’s Hypothesis:

    • Cells arise from cells

    • Cells do not arise by spontaneous generation

      • Hypothesis: Presence of preexisting cells is required for cell growth

      • Null Hypothesis: Presence of preexisting cells is not required for cell growth

      • Predictions:

        • Cell growth only observed if preexisting cells already existed

        • Cell growth observed regardless of whether preexisting cells already existed

  • Louis Pasteur’s Experiment:

    • Straight neck flask & Swan neck flask w/ broth

      • Heated up to kill any preexisting cells w/in

      • Dust particles w/ microbes entered straight neck flask, but not swan neck flask

    • Final observations:

      • Broth became cloudy from growth of microbes in straight-neck flask but remained clear (sterile) in swan-neck flask


Review - What is life?

  • What does it mean to say something is alive?

    • Common characteristics that organisms share

    • 3 most influential unifying ideas in biology:

      1. Cell theory

      2. Chromosome theory of inheritance

      3. Evolution

  • Life emerges from cells:

    • Cell theory


Chromosome Theory of Inheritance

  • How is hereditary information transmitted from generations

    • 1902 - Walter Sutton & Theodor Boveri

    • Genes: Hereditary/genetic information

      • Located on Chromosomes

      • 1950s: Chromosomes (molecules of DNA) - hereditary material

        • DNA pairing preserves info

  • Central Dogma:

    1. DNA transcribed into mRNA (copied & transmitted)

    2. mRNA translated into Proteins

  • Mistakes in DNA copying

    • Changes in proteins (mutations)

    • Outward appearance is product of proteins

      • Changes may cause changes in outward appearance (traits selection acts on - changes fitness of organism)


Review 2: What is life?

  • Life Processes Information:

    • Chromosome theory of inheritance - genes on chromosomes

      • Chromosomes = DNA = hereditary material

        • Codes for products in cell

      • Central dogma: flow of info from DNA to protein

      • Errors in replication = mutations = source of heritable variation (evolution)

Theory of evolution by Natural Selection

  • Where do organisms come from?

  • **NOTE: Natural selection acts on individuals, Evolutionary Change acts on populations

  • Speciation: Populations diverge to form new species


Timeline of Theory of Evolution Creation:

  1. Special Creation (Natural Theology) - Before Dawrin

    • All species created separately, unrelated to one another

    • Each species in unchanging, little variation w/in each

** Species: Distinct, identifiable organism

  • Challenges: Extinct species fossils

  1. Darwin & Wallace:

    • Made two claims:

      1. All species related by Common Ancestry

      2. Characteristics of species modified from generation to generation (Descent w/ modification)

        • Microevolution: Species changing over time

        • Macroevolution: Species splitting & diverging

What is Evolution?

  • Evolution: Change in characteristics of population over time

    • Species related to one another, can change through time

  • Population: Group of individuals, same species, same area, same time

  1. Adaptive (Selection)

  2. Nonadaptive(genetic drift, gene flow, mutation, non-random mating)

2 Conditions of Natural Selection:

  1. Heritability

  2. Heritable variation must help reproductive success

    • Those traits that lead to increased success in reproduction become more common in population over time

    • Population characteristics change (evolution - natural selection)
























Fitness & Adaptation

  • Fitness: Ability of individual to produce offsping

    • High fitness - more surviving offspring

    • Low fitness - less surviving offpsring

  • Adaptation:

    • Heritable trait increases fitness of individual in particular environment

Eg. Finches on Galapagos Fitness

  • Variation in finch beak size/sape

  • Rainfall became consistent - small soft seeds more abundant

    • Shift in proportion of finches w/ small, pointed beaks

  • Finches w/ small, pointed beaks had higher fitness & trait was heritable —> considered adaptation, increased ability to thrive

    • Frequency of small, pointed beaks increased in population


Lecture 3 Content:

Example of Evolution/Adaption - Daphnia

  • Lake A: No predators

    • No spines

  • Lake B: Predators

    • Predators Present

    • can develp spines through lifespine, it is an induceable mechanism

Review 3: What is Life?

  • Life Evolves:

    • Theory of evolution: all organisms related by common ancestry

    • Natural selection: Well-tested explanation for why species change through time, why so well adapted to their habitats

Characteristics of Good Experimental Design:

  1. One or more control groups to check for other factors that might influence outcome

  2. Conditions controlled to eliminate confounding variables

  3. Replicate tests to reduce effects of distortion